04/18/23 Franck DELACROIX - ADEME1
An efficient combustion device leading also to very low NOx emission levels
Franck DELACROIX
ADEME (French Agency for energy and environment management)
BAT co-ordinatorEGTEI (Expert Group on Techno Economical Issues) agency leaderSOx, NOx and N2O emissions of industrial processes
“The flameless oxidation mode” :
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NOx emission reduction : Primary techniques Optimal choice of the burner and its operating conditions Staged combustion
• Air staging
• Gas staging (reburning) Recirculation of combustion products
• Internal
• External Etc...
Energy efficiency and NOx emission reduction
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Energy efficiency : example of regenerative burners
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Energy efficiency and NOx emission reduction
Air preheat temperature
(°C)
NOx (mg/Nm3 – O2 3% -
dry gases)
100 – 200 Below 400
300 Up to 450
400 Up to 600
500 Up to 800
700 Up to 1500
800 Up to 2300
900 Up to 3500
1000 Up to 5300
Possible indicative influence of air preheat on NOx emissions
5,0
22
16
ON
T
69090exp
T
10.6
dt
NOd
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Energy efficiency and NOx emission reduction
First generation of regenerative burners with very high NOx emission levels Studies have been realized mainly in Japan, Germany and USA, Several manufacturers have commercialised new types of burners, Industrial demonstrations have been mainly validated in Asia, European references at quite small scale.
Principle of these new burners :
the „flameless combustion mode“
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THE FLAMELESS OXIDATION MODE : principle 1/2
oxidising air and fuel gas injected separately with high injection speeds,recirculations of the combustion products to the burner high temperature of the recirculated combustion products (> 1000°C) used to initiate and maintain this mode of “combustion”.
AIR
GAZ
Recirculation
Recirculation
AIR
GAZ
Recirculation
Recirculation
Process heat
I II
III
Air
Gas
Combustion products
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THE FLAMELESS OXIDATION MODE : principle 2/2
combustion distributed throughout the volume of the combustion chamber, relative homogeneity (temperature and composition) in the combustion chamber, the flame can then no longer be seen,
Explaining why experts of this field speak about :
THE FLAMELESS OXIDATION OR COMBUSTION MODE
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How to characterize the FLAMELESS OXIDATION MODE
and explain the low NOx emission level ?
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The INTERNOx project
Three years project started in October 2000 Partners : Gaz de France, Arcelor/IRSID, Stein-Heurtey and supported by ADEME
Containing the following phases : - Technological survey,
- Study of the heating equipments,- Design of pre-dimensioning tools dedicated to slab furnaces,- Study at semi-industrial scale,- Validation of the simulation tools,- Preparation of a demonstration project at industrial scale.
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Main goals of the study
Energy savings• Improvement of energy efficiency• Optimisation of processes
Pollution reduction• CO2
• NOx• Noise
Product quality Process reliability
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Burner characterization
• WS GmbH (Germany)• North American Manufacturing Co (US)• NFK (Japan)• Etc
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NOx : Influence of the main operating parameters
0
100
200
300
400
500
600
700
800
900
1000
1000 1050 1100 1150 1200 1250 1300 1350 1400
T furnace (°C)
NO
x (m
g/m
3(n)
@ 3
% O
2)
0
100
200
300
400
500
600
700
800
900
1000
0 100 200 300 400 500 600 700
Thermal input (kW)
No
x (m
g/m
3(n
) @
3%
O2)
0
100
200
300
400
500
600
700
800
900
1000
0,7 0,9 1,1 1,3 1,5 1,7
Air ratio
No
x (m
g/m
3(n
) @
3%
O2)
0
100
200
300
400
500
600
700
800
900
1000
40 50 60 70 80 90
Exhaust gases through burner
No
x (m
g/m
3(n
) @
3%
O2)
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Main conclusions of the burner tests
Very Low NOx burners commercially available : NO <300 mg/m3(n) and η > 75% whatever the operating conditions,
Strong influence of the air-fuel ratio on NOx emissions, Influence of the furnace temperature on NOx and combustion
efficiency Low effect of thermal input on NOx Strong influence of the percentage of exhaust gases through
the burner on the combustion efficiency Design tools necessary to implement this new combustion
technique (product quality, efficiency, …)
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Other studies of the heating equipmentDetailed measurements in the flame
Parameters followed
• temperature
• species
• velocity
• heat transfers
Reference operating conditions
• thermal input = 200 kW,
• preheated air = 1000 °C
• furnace temperature = 1300 °C
• air / fuel ratio = 1,1
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Study of the heating equipmentDetailed measurement in the flame – main results
Fields of the mean temperatures
Chemiluminescence emission of the OH* radical
Fields of CO concentration and mean temperatures
m i n m a xm i n m a xm i n m a x
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Simulation of the flameless combustion mode
Pre-dimensionning of slab reheating furnaces
Existing software has been adapted by the Polytechnic Faculty of Mons and IRSID to simulate the installation of burners working in the flameless combustion mode into any area of a furnace.
Considering the stationary regime, this tool showed that :- a decrease in fuel consumption by 8,5% can be expected installing this new type of burner in the preheating zone of an existing furnace instead of conventional burners,- the design of a new furnace only fitted with this kind of burner could increase the productivity by 17% and decrease the fuel consumption by 14% .
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Simulation of the heating equipment and representation simplification
CFD approach has been chosen The methodology employed is:
• to pre-select the sub-models used to represent the industrial burners • to validate them with the detailed in-flame measurements
■ Simplification : accuracy/calculation-time compromise, in relation to the detailed model,
Conclusions implemented to simulate the test furnace at semi-industrial scale in the dynamic regime
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Test at semi-industrial scale and validation of the tools
Objectives:• to validate the modeling tools developed in parallel• to assess the performance of the flameless-oxidation burners in
conditions close to an industrial furnace• to acquire a technical expertise to scale up this technology in the
industry
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The combustion efficiency is over 85% in the reference operating conditions
The pulsed regulation mode is very good for the burners control (in terms of heating quality and NOx emissions)
The burners enable to achieve a very good thermal homogeneity These tests represent a very useful database for the validation and
the specification of the simulation tools limits
Test at semi-industrial scale and validation of the tools
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Soaking zone
Heating zone
Billets entrance
Billets exit
Objectives : production capacity increase, while improving efficiency and reducing NOx emissions.
Existing slab reheating furnace
CFD assessments showed that the installation of two pairs of 3MW burners upstream the heating zone gives the most interesting results
Preparation of a demonstration project at industrial scale
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Preparation of a demonstration project at industrial scale
Mean temperature fields
Example of simulation for the reheating furnace
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Conclusions & perspectives 1/2
Regenerative burners used in the flameless combustion mode are high-performance systems allowing to significantly increase the productivity as well as reduce the CO2 emissions,
Measurements have also shown that low NOx emissions can be achieved ( below 300 mg/m3(n) at 3% of O2), whatever the operating conditions,
Several manufacturers are now offering this type of burner, Industrial demonstrations in Europe, in various sectors especially
metallurgy, should appear in the coming months, The design tools developed in the framework of the INTERNOx project ,
but also a better understanding of the combustion phenomena enable guarantees to be given regarding the performances and heating quality of the products,
It is very likely that this new combustion mode will also be used, in the short or medium term, in other industrial sectors such as ceramics, glass-making, petrochemicals, gas turbines or industrial boilers.
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Conclusions & perspectives 2/2
In the medium term, it will be thus a concern less during the BAT determination process, as it will no more be necessary to make a trade-off between energy efficiency, productivity and NOx emission reduction...
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Thank you for your attention